Roll googletest to 1.8.0.

testing/gmock_custom/gmock/internal/custom/gmock-port.h

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef TESTING_GMOCK_CUSTOM_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
-#define TESTING_GMOCK_CUSTOM_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_
-
-#include <type_traits>
-
-namespace std {
-
-// Provide alternative implementation of std::is_default_constructible for
-// old, pre-4.7 of libstdc++, where is_default_constructible is missing.
-// <20120322 below implies pre-4.7.0. In addition we blacklist several version
-// that released after 4.7.0 from pre-4.7.0 branch. 20120702 implies 4.5.4, and
-// 20121127 implies 4.6.4.
-#if defined(__GLIBCXX__) &&   \
-  (__GLIBCXX__ < 20120322 ||  \
-   __GLIBCXX__ == 20120702 || \
-   __GLIBCXX__ == 20121127)
-template <typename T>
-using is_default_constructible = std::is_constructible<T>;
-#endif
-
-}
-
-#endif  // TESTING_GMOCK_CUSTOM_GMOCK_INTERNAL_CUSTOM_GMOCK_PORT_H_